Forces loyal to the Arab coalition have been trying to consolidate power over the central province of Marib, east of the capital, in an apparent bid to advance on Sanaa, which remains under the control of Iran-backed Houthi rebels.

The governor of Marib told Al Jazeera on Monday that forces allied to President Abd-Rabbu Mansour Hadi and the Gulf coalition were "perusing the last pockets of Houthis" in the province.

Sultan al-Arada said the security committee of the province issued a number of measures to secure the roads leading to the Marib, including the international road.

Pro-Hadi forces advanced in Marib after pushing the rebels out of five southern provinces, including the port city of Aden to which the government returned last month after six months in exile.

Warplanes belonging to the coalition on Monday launched air strikes on Houthi targets in Taiz, the country's third city, including the medical college near the presidential palace and the 35th Brigade headquarters in the old airport.

Houthis, after they overran Sanaa unopposed in September last year, widened their control to several Yemeni provinces, advancing in March on Aden where Hadi had taken refuge before fleeing to the Saudi capital, Riyadh.

The coalition then launched a fierce air campaign in March against the Houthis and their allies to loyal to the former president, Ali Abdullah Saleh.

The coalition has come under mounting criticism over the civilian death toll in its campaign.

Last week, the UN undersecretary-general for humanitarian affairs, Stephen O'Brien, called for a swift investigation of a suspected deadly air strike on a wedding in Dhamar province the day before.

Medical sources said at least 28 people were killed while the Houthi-controlled Saba news agency said 51 died. The coalition has categorically denied any bombing there.